The technical problem raised is that of tracking the positions of vehicles travelling in convoys. The lead vehicle can be driven by a driver. One or more vehicles of the convoy can be driven automatically. The distances observed between vehicles are typically of the order of ten or so meters. Since the reaction time of one vehicle to the next is linked to the measurement time and to the communication time between vehicles, reaction times of 0.1 second can be accessed. At 40 m/s (145 km/h), this corresponds to a minimum distance of 4 meters between pairs of vehicles (the distance has to be kept to the minimum to avoid the appearance of undetectable obstacles or events between two vehicles, for example an animal crossing the road).
This technical problem arises mainly in the context of routine following. In critical conditions (emergency braking for example), the detection of the actions of the first driver and the reactions of the first vehicle can be done by means of sensors suited to these critical phases (notably odometers), conservative strategies then being able to be envisaged. However, these dedicated sensors do not have a resolution and a stability that is sufficient for routine measurements.
The state of the art discloses very few methods that make it possible to solve this technical problem and the results are generally not satisfactory. For example, some techniques use artificial vision and/or ground marking following systems (for example RFID chips inserted into the roadway). These methods require heavy and costly instrumentation or are not flexible.
One solution consists in synchronizing the clocks of the different vehicles, for example on their departure (and/or in compensating the drifts of these different clocks over time). The measurement of the communication times between the vehicles divided by the speed of light would then theoretically make it possible to deduce the separating distances between vehicles. In reality, this approach does not work, given the clock drifts that are commonly observed (the distance error is then around 10 or so meters).
There is an industrial need for processes and methods that make it possible for convoys of vehicles to travel in safety, particularly outside of the major highways.